The present invention relates to a golf club head. More specifically, the present invention relates to a hollow, wood golf club head.
With wood golf clubs such as drivers, spoons, and brassies, the flight distance and directional control over the golf ball is considered important. It is known that the flight distance and directional control are affected by the moment of inertia around the center of gravity of the golf club head. The moment of inertia increases as the volume of the golf club head increases. As a result, hollow golf club heads made from metal materials, such as stainless steel, titanium alloy, and high-tensile aluminum alloys have become prominent among wood golf club heads. This, in part, is due to the higher moments of inertia which are possible with hollow golf club heads. As a result, the golf club heads themselves have become larger (e.g., Japanese laid-open patent publication number 4-256764).
A hollow golf club head provides for a longer flight distance, a larger xe2x80x9csweet spotxe2x80x9d, and reduced veering in the flight path when compared to previous solid-core heads such as persimmon heads. However, the large specific gravity of the metals used in conventional hollow golf club heads places a limit, from the standpoint of strength, on the degree to which the moment of inertia of the entire club head can be increased by increasing the volume of the hollow section of the club head.
It is an object of the present invention to provide a golf club head which overcomes the drawbacks in the prior art.
It is another object of the present invention to provide a golf club head which has a large moment of inertia.
It is yet another object of the present invention to provide a golf club head which is well suited for use in a golf club such as a driver.
It is still another object of the present invention to provide a golf club head which has a large moment of inertia, while maintaining adequate strength for use in a driver type golf club.
It is a further object of the present invention to provide a hollow golf club head with a large moment of inertia while maintaining adequate strength for use in a driver type golf club, in which the veering of the flight path and the corresponding loss in distance is very small.
It is yet a further object of the present invention to provide a hollow golf club head which minimizes veering in the flight path of a golf ball and also minimizes the corresponding loss in flight distance due to veering.
It is an object of the present invention to provide a hollow golf club head in the form of a hollow head that is made from a material having a specific strength of at least 30 kg/mm2 and that has a moment of inertia around a perpendicular axis passing through the center of gravity when the head is at a standard usage position of at least 4xc2x710xe2x88x924 kgxc2x7m2. It is desirable for the weight of the golf club head described above to be no more than 200 g, the volume of the golf club head to be in the range from 300 to 900 cc, and the thickness of the face of the head to be at least 4 mm. Furthermore, it is desirable to have a metal fiber paper and/or a metal film layered on the exterior surface of the head. It is also desirable to use a bidirectional carbon fiber reinforced epoxy resin or the like for materials having a specific strength of at least 30 kg/mm2.
Briefly stated, a hollow golf club head provides for a longer flight distance, a larger xe2x80x9csweet spotxe2x80x9d, and reduced veering in the flight path than a conventional golf club head. The golf club head has a maximum weight of 200 g, a volume in the range from 300 to 900 cc and a moment of inertia of at least 4xc2x710xe2x88x924 kgxc2x7m2. The head is made from a fiber reinforced epoxy resin which provides at least 30 kg/mm2. Suitable reinforcing fibers include carbon fiber, fiberglass, aramid fiber and polyester fiber. Suitable resin materials include epoxy resin, unsaturated polyester resin and vinyl ester resin. The reinforcing fibers in the resin are arranged such that adjacent layers of reinforcing material are oriented perpendicular to one another. The perpendicular orientation of the fibers provide shock resistance to the head. A high elasticity and high density component, such as tungsten, is dispersed in the resin to provide reduced vibrations and improved acoustics to the head when impacting a ball. The outer layer of the head can be made from a metal material, such as titanium, to minimize damage to the face and the sole of the head due to friction. The club head is formed by: cutting fiber prepregs into a specified shape, placing the cut fiber prepregs into a two-piece concave mold such that the fibers in adjacent layers are aligned perpendicular to one another, closing the two-part concave mold around a nylon tube bag, pressurizing the nylon tube bag as the closed two part mold is heated to 130xc2x0 C. for 1 hour, and splitting the mold open after heating to provide a hollow golf club head.
According to an embodiment of the invention, there is provided a hollow golf club head comprising a material having a specific strength of at least 30 kg/mm2 wherein a moment of inertia around a vertical axis passing through a center of gravity when the head is in a usage position is 4xc2x710xe2x88x924 kgxc2x7m2.
According to another embodiment of the invention, there is provided for a golf club head comprising a carbon fiber, bidirectionally reinforced epoxy resin material with a specific strength of at least 30 kg/mm2 wherein a moment of inertia around a vertical axis passing through a center of gravity when the head is in a usage position is 4xc2x710xe2x88x924 kgxc2x7m2, the head having a maximum weight of 200 g, the head having a volume in a range from 300 to 900 cc, the head having a face with a minimum thickness of 4 mm and an exterior surface of the head is layered with a metal fiber material with a plurality of openings.
According to yet another embodiment of the invention, there is provide for a hollow golf club head for striking a golf ball when the golf club head is in a usage position, comprising: a composite material formed in a shape, the composite material having a specific strength in a range from 30 to 60 kg/mm2, and a moment of inertia around a vertical axis passing through a center of gravity of the golf club head when the golf club head is in the usage position.
According to an embodiment of the invention, there is provide for a hollow golf club head for striking a golf ball when the golf club head is in a usage position, comprising: a composite material formed in a shape, the composite material having a specific strength in a range from 30 to 60 kg/mm2, a moment of inertia around a vertical axis passing through a center of gravity of the golf club head when the golf club head is in the usage position, the moment of inertia is at least 4xc2x710xe2x88x924 kgxc2x7m2, the golf club head having a minimum volume of 300 cc, the composite material having a head thickness of at least 3 mm, and the composite material including a bidirectionally reinforced matrix resin having an amount of reinforcement material dispersed therein in a range from 40% to 70% of a total volume of the matrix resin.
According to a method of the present invention, there is provided a method for forming a hollow golf club head, the steps comprising: cutting a metal film material to form a shaped metal material, cutting a first fiber reinforced resin material to form a first shaped material, cutting a second fiber reinforced resin material to form a second shaped material, placing the shaped metal material on inner surfaces of a two-piece concave mold, placing the first shaped material on the shaped metal material while the shaped metal material is in the concave mold, placing the second shaped material on the first shaped material while the first shaped material is on the shaped metal material in the concave mold, such that fibers in the first and second shaped materials are oriented in a direction perpendicular to one another, placing a nylon tube bag on the second shaped material such that when the two-part mold is closed the nylon bag remains within the closed mold while the tube extends out of the concave mold, closing the concave mold with to form a closed mold, the closed mold having a tube extending out of the concave mold, forcing air at a pressure of 4 kg/cm2 through the tube into the nylon bag inside the closed mold to form a pressurized mold, heating the pressurized mold at a temperature of 130 C. for 1 hour, and splitting the pressurized mold open after the step of heating to provide the hollow golf club head.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.